A conventional motor for a power window device or the like includes a motor body, which rotates and drives a rotation shaft, and a reduction drive, which serves as a rotation transmission device including a worm gear that reduces the rotation speed of the rotation shaft. Such a reduction drive may include a worm wheel coupled to an output shaft by a buffer mechanism. Patent document 1 discloses an example of a buffer mechanism including an elastic member and a transmission plate. In patent document 1, a worm wheel includes a plurality of engagement portions arranged at equal angular intervals in the circumferential direction. The elastic member includes two dampers arranged to contact the two circumferential ends of each engagement portion. The transmission plate includes an engagement bulging portion that is bulged to cooperate with the engagement portions to sandwich each damper in the circumferential direction. Further, patent document 1 describes a further transmission plate including an engagement piece bent from a metal plate in lieu of the engagement bulging portion. A single engagement bulging portion or a single engagement piece is arranged between the dampers that are adjacent in the circumferential direction and shared by the dampers.
In such a motor, the rotation force of the worm wheel (engagement portions) is transmitted to the transmission plate (engagement bulging portion or engagement piece) by the dampers. This rotates the output shaft coupled to the transmission plate. In such a motor (rotation transmission device), the dampers are elastically deformed to dampen the impact produced when a sudden load is applied to the output shaft (transmission plate) during, for example, rotation of the worm wheel.